The IP (Internet Protocol) Multimedia Subsystem (IMS) is an Internet based technology within the service provider wireless network which communicates with a mobile station over a standard data pipe provided by the Universal Mobile Telecommunications System (UMTS) packet data system, a third generation packet telecommunications system. IMS can also be used with other wireless technologies such as Wi-Fi (wireless local area network products based on the IEEE 802.11 specification) and North American CDMA. For setting up connections, a client server model is used between the mobile station and the IMS network element called the Call Session Control Function (CSCF). Session Initiation Protocol (SIP) messages are used to configure the call. After session setup, IMS becomes a peer-to-peer communication directly between the mobile station and another IMS capable endpoint. This means that the wireless data transport system such as the UMTS packet data system is used merely to transport data, and under current standards does not have knowledge of the contents of IMS related SIP messages. CALEA and legal intercept laws require a service provider to provide call content and to make possible the correlation of CSCF SIP messages with this call content.
A problem of the prior art is that the arrangements for providing the required information to the CALEA/Legal Intercept collection function of law enforcement provides the CSCF SIP messages by a different path than the bearer content of the peer-to-peer communication messages since the CSCF SIP messages are forced to traverse the Internet before reaching the CALEA/Legal Intercept collection function. This delay makes it difficult to correlate bearer content with specific call arrangements contained in the CSCF SIP messages. The delay also makes it impossible to perform real time extraction from the bearer stream of specific services such as Voice over IP (VoIP) that are of great interest to law enforcement. With the prior art all services must be delivered to law enforcement possibly in violation of court orders.